The Antibody Therapy Unit in the Laboratory of Molecular Biology was started on May 25, 2008. My laboratory conducts mechanistically-based, translational research leading to the development of novel and more effective anti-cancer antibody therapies. Our efforts are currently focused on developing new mAbs directed at ovarian cancer and mesothelioma. This work is currently supported in part by the Intramural Research Program of the NIH, National Cancer Institute, Center for Cancer Research, in part by the Ovarian Cancer Research Fund Individual Investigator Award (M. Ho) and in part by the Mesothelioma Applied Research Foundation Grant in Honor of Craig Kozicki (M. Ho). Biology of Ovarian Cancer and Mesothelioma - Cancer cells commonly spread within the peritoneal cavity via seeding to mesothelium-lined structures. The interaction between CA125, a mucin present on a majority of ovarian cancer and mesothelioma cells, and mesothelin, a GPI-anchored glycoprotein present on the mesothelial cells lining along the peritoneal cavity, has been suggested to facilitate implantation and metastasis of tumors. We hypothesize that blocking the mesothelin-CA125 interaction may prevent or reverse metastasis and lead to overall improved survival in cancer patients. A better understanding of how these two proteins interact may eventually aid in developing such as therapy. To this end, my laboratory is now vigorously investigating the biological mechanisms underlying the molecular interaction of mesothelin and CA125. (1) We have successfully identified the binding site on mesothelin for CA125. We have identified specific amino acids within the CA125-binding site of mesothelin that are involved in the interaction with CA125. (2) We have developed the antibody-like Fc fusion molecules containing the CA125-binding site. Studies by my laboratory have shown that the Fc fusion proteins can effectively block the binding of mesothelin to CA125, suggesting the CA125-binding domain could be used as an antagonist to inhibit tumor progression and spread in peritoneal cavity. (3) We are characterizing the yet unidentified mesothelin-binding site on CA125 which likely contains a novel N-glycan structure as suggested by our previous studies. Antibody Therapy - We are conducting translational research leading to the development of antibody therapeutics for cancer treatment. (1) We are isolating and characterizing several mouse and human mAbs specific for mesothelin. The studies by my laboratory have recently found the single chain Fv mAb that can effectively blocks the mesothelin-CA125 protein-protein interaction and whose epitope overlaps the CA125-binding site. We are using antibody engineering technologies to develop human or humanized antibodies for peritoneal cancer treatment. (2) In order to evaluate the efficacy of the CA125-binding domain Fc fusion proteins for peritoneal cancer therapy, my laboratory is in the process of initiating preclinical studies developing peritoneal xenograft models of ovarian cancer and mesothelioma in mice. We are currently making recombinant domain Fc fusion proteins and developing the cancer cell lines used for tumor imaging in animal studies. The animal protocol for preclinical studies is currently undergoing Animal Care and Use Committee (ACUC-Bethesda) review in the NIH. (3) We have established a new antibody engineering method, called mammalian cell display. Functional single chain Fv antibodies (scFv) can be expressed on human cells and high affinity scFv binders can be rapidly identified and isolated from a combinatory Fv library. Utilizing this new technology, we are currently improving binding affinity of therapeutic antibody Fvs for better efficacy in cancer targeted therapy. (4) We have initiated the construction of a new human Fv antibody library in human HEK-293 cells utilizing our new-developed mammalian cell display technology for antibody discovery. (5) We have established an ELISA assay in my laboratory to examine humoral (antibody) response to mesothelin in ovarian cancer and mesothelioma. In a phase I clinical trial of single-dose intrapleural IFN-beta gene transfer for malignant pleural mesothelioma and metastatic pleural effusions, we found high rate of antitumor immune responses directed to mesothelin. We will continue investigating the anti-tumor immune (particularly antibody) response directed to mesothelin in cancer patients and studying how the immune response against cancer-specific antigens is relevant to improved clinical outcomes.